1. Technical Field
The present invention relates to a belt for a continuously variable transmission used in, for example, a belt type continuously variable transmission of an automobile.
2. Related Art
A belt used in a belt type continuously variable transmission is constituted by holding a number of elements by a ring in an endless shape. For example, as shown by FIG. 10 (a), an element 140 comprises an ear portion 142, a neck portion 143 and a body portion 144. Thick-walled portions 142a, 144a are formed at the ear portion 142 and the body portion 144, respectively. The vibration of belt is prevented by contacting the thick-walled portions 142a, 144a with the element 140 disposed on a front side thereof (refer to, for example, JP-UM-B-5-37067).
However, in the belt 107 with the above-described structure, the contact of the element 140 with the element 140 disposed on the front side thereof is restricted by the thick-walled portions 142a, 144a formed at the ear portion 142 and the body portion 144. Therefore, as shown by FIG. 10 (b), a rigidity of a pushing side chord portion N of the belt 107 in a belt advancing direction cannot be sufficiently ensured and the vibration of belt is generated. Further, at a high belt peripheral speed, the pitching of element 140 is produced at an outlet of a drive pulley by advancing an outer side of the element 140 faster. When the thick-walled portions 142a, 144a are formed at the ear portion 142 and the body portion 144, it is impossible to prevent the vibration of belt which is caused by the pitching of element 140 produced at the high belt peripheral speed. Further, also at a wrapping portion of the belt 107, when the element 140 is urged such that its V face becomes orthogonal to the pulley, in the case in which a plate thickness difference is produced within a locking edge portion 145 of the body portion 144, the locking edge portion 145 cannot stably be brought into contact with a rear face of the element 140 on the front side and there is a possibility of accelerating wear of the V face.
Further, as shown in FIG. 8(a), since there is no contact point at the neck portion, the effective radius dT for bending moment can not be made to the sufficient value. Therefore, the pitching of the body portion is prevented mainly by bending moment of the neck portion with one portion in the center of the body portion and the locking edge portion as a center, and thus, it is difficult to prevent completely the pitching of the body portion.